AIDS (acquired immune deficiency syndrome) is a serious social problem spread over the world as a refractory viral disease caused by HIV and the research and development of anti-HIV drugs have been undertaken on a worldwide scale. To this day, nucleic acid derivatives such as azidodeoxythymidine (AZT), dideoxyinosine (DDI), dideoxycytidine (DDC), dideoxydidehydrothymidine (D4T), and 3'-thiacytidine (3TC) have been developed as major target and put to use clinically, but severe adverse reactions and decreace of the efficacy due to occurrence of resistant strains have produced new problems and, therefore, the development of new therapeutic drugs has been eagerly awaited.
The pathologic picture of AIDS has not been fully elucidated yet, and recently it has been found that even in asymptomatic patients whose clinical stage is considered to be at a latent period, virologically the virus is actively proliferated in the lymph node. Therefore, development of an improved anti-HIV drug is an important social need today.
Meanwhile, explorations into various imidazole derivatives have been undertaken with the view of utilizing them as medicines.
U.S. Pat. No. 3,968,228 describes imidazole derivatives effective for the therapy of coccidiosis in animals as well as a variety of imidazole derivatives as intermediates for their synthesis. In the imidazole derivatives disclosed, however, the substituent attached directly to the imidazole ring via a --S--, --SO--, or --SO.sub.2 -- moiety is limited to alkyl groups.
U.S. Pat. No. 4,592,774 discloses imidazole derivatives which are of use as herbicides. However, all the disclosed imidazole derivatives necessarily have an opionally substituted phenylmethyl in the 2-position of the imidazole ring.
Japanese Kokai Hei-2-83373 discloses a series of imidazole derivatives of value as agrochemicals, medicines, perfumes, or polymer materials. These imidazole derivatives are substituted by hydrogen, cyano, carbamoyl, thiocarbamoyl, or a group of the formula COOR.sup.2 (those represented by substituent Y in the publication) in the 4- and/or 5-position(s).
Japanese Kokai Hei-5-252270 describes imidazole derivatives having anti-HIV activity. In the disclosed imidazole derivative, however, the substituent in the 1-position of the imidazole ring is limited to groups of the formula --(CH.sub.2)n--O--R.sub.3 having an ether linkage.